Glaze defect where fired glaze surface contains bubbles, which often break open to leave sharp-edged craters in surface. Most often caused if volatization of materials in clay and glaze is still occurring when kiln is shut off, freezing bubbles in place. Best solution in high-firing is brief oxidation soak at end of firing to allow surface defects to heal. Same may be accomplished in low-firing by slowing down firing or by soaking kiln near maturation. Source: Clay: A Studio Handbook

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